A study on factors that affect error rates in handwriting examinations of Korean characters by forensic document examiners and non-experts

Abstract

Forensic handwriting examinations are often considered important in trials, and especially those related to property issues. There is also increasing demand by courts for the quantification of handwriting examination results. Notably, in forensic science, error rates in forensic handwriting examinations should be carefully quantified in order to ensure their reliability as evidence. The present study examined error rates in forensic handwriting examinations conducted by both forensic document examiners (FDEs) and non-experts. To this end, four FDEs affiliated with forensic science institutes and a group of 20 laypersons were asked to perform a forensic handwriting examination of Korean characters in various forms (long text, short text, and signature samples) in blind test settings; i.e., specific information about the test was not given. The test was composed of 180 questions. The results showed that the incorrect answers are much higher in the non-expert group than the expert group though; however, the percentage of "inconclusive opinion" answers was higher in the expert group. It was also found that, in the expert group, error rates could be lowered by allowing a joint examination (or a peer review) to be performed. Meanwhile, the expert group showed relatively high error rates when dealing with handwriting samples simulated or disguised, rather than those that contained a small number of characters, such as signature samples. In the non-expert group, financial reward did not contribute to increasing the correct answers (%) of handwriting examination but rather encouraged examiners not to choose "inconclusive opinion" answers. This result indicates that a financial reward may unintentionally affect the examination results. The major findings of the present study are of significance in that this study is the first attempt to specifically examine error rates in forensic handwriting examinations of Korean characters conducted by both expert and non-expert groups. This study also demonstrated that the exchange of opinions among FDEs affected the resultant error rates and overall examination results. It was also found that financial reward may affect handwriting examination results as well.

Keywords: Blind test; Experts; Forensic document examination; Handwriting; Non experts.